gmail SMTP fails with T-Mobile home network

Could the issue be this?

SMTP blocked via Spamhaus | Comunidad de T-Mobile

jservi wrote:

I recently switched to T-Mobile Home Internet.  I'm very pleased with the service, but every now and then I am unable to send email via my non-TMO email provider.  It is an IMAP account and sends email via smtp, but NOT port 25 of course.  Port 25 is typically blocked to prevent spammers from using dynamically assigned IP addresses, nothing unusual.  Since TMO's network is an IPv6 network, I've figured out that a translation technology (464XLAT) is implemented to provide IPv4 connectivity to users, this is a common technology for this purpose.  However, this solution translates many users into a pool of IPv4 addresses rather than providing a 1:1 IPv4 address.  The outbound IPv4 address that it appears I use, is also used by many other users.

I am not a spammer, but as a result of this common translation technology, I'm sharing that IPv4 address with users who apparently are spammers.  From time to time I am getting blocked from sending my legit smtp email because the Spamhaus service sees spam connections from that shared IPv4 address.  An example of a recent report from Spamhaus:

172.58.47.103 is listed in the Spamhaus XBL

Why was this IP listed?

A device (computer, server, mobile phone, etc), or an app on a device that is using 172.58.47.103 is infected, insecure or compromised. It is making SMTP connections with forged HELO values on port 25.

The observed forged HELO value was vvt.nox.ticl.saaxeaxewhikow.com. The most recent detection occurred at: January 22 2021, 12:55:00 UTC (+/- 5 minutes)

 

I've done packet captures on my home network.  I know these smtp connections are not coming from my network.

I can request Spamhaus remove the IP address from their blocklist which will allow me to send email, but it is only a matter of time before I get blocked again.

 

I’d like to know if there is a permanent solution for this issue.

 

Gracias,

JS

 

When checking my IP4 address on Spamhaus it says the below.  Not sure what "designated outboud mail server allocated to T-Mobile..." means though.
 

Outbound Email policy of T-Mobile US for this IP rangeIt is the policy of T-Mobile US that unauthenticated email sent from this IP address should be sent out only via the designated outbound mail server allocated to T-Mobile US customers by their email provider (Hotmail, Gmail, ...). To find the hostname of the correct mail server to use, customers should consult the original signup documentation for their email account or contact their email provider.